1. Field of the Invention
The present invention relates to a centrifuge instrument and a centrifuge rotor for use therein for centrifuging a sample of a liquid in preparation for subsequent analysis, and more particularly, to an instrument and rotor able to load and unload automatically a container having a sample therein.
2. Description of the Prior Art
Currently, prior to analysis, it is the practice in some standard laboratory procedures to use centrifugal force to separate a liquid sample, such as a sample of a body liquid (e.g., blood) into various fractions in accordance with their differing density. The sample of liquid is carried in a container, such as a test tube, which is inserted into a centrifuge rotor. The rotor is mounted on the upper end of a shaft that projects upwardly into a chamber, or bowl. The bowl is supported on the interior of the housing of the centrifuge instrument. The shaft is connected to a motive source which, when activated, rotates the rotor to a predetermined rotational speed. Centrifugal force acts on the sample carried within the container and causes the components thereof to separate in accordance with their density.
Since in a typical laboratory setting it may be necessary to separate a relatively large number of samples within a given time period, manual loading and unloading of the sample containers into a centrifuge rotor may require an inordinate amount of time. Moreover, during handling of the sample containers the potential exists that an operator may be exposed to the sample if an accident occurs or if the container is damaged or mishandled. Accordingly, the prior art has developed various robotic devices for automatically loading and unloading sample containers into a centrifuge rotor.
U.S. Pat. No. 5,171,532 (Columbus et al.) discloses an analyzer having an incubator and a centrifuge instrument therein. The centrifuge rotor rotates about a horizontal axis. Owing to the horizontal orientation of the axis of rotation sample containers are mechanically inserted into and mechanically pushed from the rotor in a horizontal direction.
U.S. Pat. No. 4,501,565 (Piramoon) discloses a gravity feed apparatus for locking a bucket onto the trunnion arms of a swinging bucket centrifuge rotor.
U.S. Pat. No. 3,635,394 (Natelson) describes a system having clothes pin-like clamps for loading and unloading sample containers to and from a centrifuge rotor. The containers are presented to and carried away from the respective loading and unloading clamps on respective first and second conveyors.
U.S. Pat. No. 4,927,545 (Roginski) discloses a robotic gripper designed to load blood tubes into a centrifuge rotor. The tubes are brought to the gripper on a first carrier. After centrifugation the gripper removes the tubes from the rotor and places them into a second carrier.
U.S. Pat. No. 4,685,853 (Roshala) describes a manual tool used as an aid in sequentially loading microelectronic components from a carrier stick into an insert in the rotor of a centrifuge. After the centrifuging operation the insert is removed from the rotor and the manual tool is used to return the components into the carrier stick.
U.S. Pat. No. 5,166,889 (Cloyd) discloses a robotic arrangement that grasps a rotor loaded with sample containers and transfers the rotor onto and from the shaft of a centrifuge instrument.
Accordingly, in view of the foregoing it is believed to be advantageous to provide a centrifuge instrument which uses gravitational force both to load each of a plurality of sample containers into a centrifuge rotor and also to unload the sample containers from the rotor after centrifugation.